Add per-builder build events to IResourceChangeEvent

# Summary

Today the resources framework only fires workspace-level PRE_BUILD and POST_BUILD events.
Listeners learn that a build ran and get the aggregated delta, but they cannot see which builder ran, on which project, for which build kind, or how long each individual builder took.

This proposes two new event types, PRE_PROJECT_BUILD and POST_PROJECT_BUILD, fired once per builder execution and nested inside the surrounding workspace PRE_BUILD/POST_BUILD pair.

# Benefits:

- Per-builder profiling. Tools can attribute build time to a specific builder and project instead of a single opaque workspace total, making it easy to spot the slow builder in a large reactor.
- Monitoring and diagnostics tooling. The granularity enables build-monitor views and telemetry that show the real build sequence, which the aggregate events cannot support.

# Performance impact

Negligible by default.

When no listener is registered, dispatch is a single hasListenerFor bitmask check per event with no allocation, so normal builds are unaffected.
The per-builder path also skips resource-delta computation entirely, so even with a listener attached the added work is cheap metadata dispatch (project, builder id, build kind) rather than tree/delta building.

# Compatibility

The change is a binary-compatible API addition (new int constants plus a default method), so existing listeners are unaffected.

Start by locating IResourceChangeEvent and the existing workspace PRE_BUILD/POST_BUILD dispatch in the resources framework. Trace how builder executions expose the project, builder identity, build kind, and timing, then verify that the new per-builder events nest within the workspace events and preserve the stated compatibility and no-listener behavior.

Written by the indexing model from the issue text.